halogenated analogs of thymidine
Vladimir I. Stobetsky
sto at aha.ru
Sat Mar 14 10:59:23 EST 1998
Key words: halogenated analogs of thymidin, human lymphocytes, allocyclic
Cytogenetic abnormalities in cultured human lymphocytes under treatment
with halogenated analogs of thymidine
After prolonged co-treatment of heteroploid Chinese hamster cells with
colcemid, that induced cells with micronuclei, and halogenated analogs of
thymidine (HAT) such as 5-iododeoxyuridine (5-IdU), 5-bromodeoxyuridine
(5-BrdU) and 5-chlorodeoxyuridine (5-ChldU) were discovered dicentric
chromosomes formed by "end-to-end fusions" (Stobetsky,1976). Registered
dicentrics were a result of delayed disruption of telomeric links existed
in interphase nucleus
In this study we investigated the cytogenetic abnormalities in cultured
human lymphocytes under treatment with low doses HAT. Scheme of experiments
In experiments we used peripheral blood of healthy donors - man at the
age 44 years an woman at the age 35 years. We added to 0,5 ml heparinized
blood 0,2 ml PHA , 6,0 ml Eagle medium and 1,5 ml calf serum. The cells
cultured at 37o C. HAT (20 microg/ml) administrated at 48 h of
for 20 h. The cells treated with colcemid (0,1 microg/ml) during last 1,5
Chromosome reparations made with standard method. In each case we scored
Most frequently we observed the delay of spiralization in the region of
constitutive heterochromatin in chromosome No9.
Table No1.Frequency of chromosome abnormalities in human lymphocytes under
treatment with HAT.
Type of abnormality Intact culture 5-IdU 5-BrdU 5-ChldU
1.Metaphases with delay spiralization or break in heterochromatin region of
chr.9. 0 27 5 1
2.Metaphases with onechromatid break or gap (except chromosomes 1,9 and 16)
3 4 5 9
1. 0 43 12 7
2. 2 1 4 10
Table 1 shows that first abnormality have a maximum under treatment with
5-IdU and minimum under action of 5-ChldU for man and
woman.Heterochromatic region of chromosome 9 look like as prophasic or
as "pulverization". Sometimes this region appeared as a break i.e.
was achromatic. This table shows also that frequency of onechromatid
breaks increased in he row 5-IdU - 5-BrdU - 5-ChldU. Locus of delay
spiralization of the chromosome 9 we consider as allocyclic chromosome
as it is or in early prophase or in S-phase i.e. such chromosomes are
allocyclic ( The behavior of allocyclic chromosomes in Bloom's syndrome.
Otto P.G. Otto P.A. and Eeva Therman. Cromosoma,1981,84:337-344). So HAT
(particularly 5-IdU) induces the shift some phases of mitotic cycle. In
favour of this hypothesis we have found some cases of "pulverization" of
whole chromosome. Intensity of this process depends directly from
molecular weight of HAT. We consider that the delay disruption of
telomeric links in cells with micronuclei in heteroploid Chinese cell
lines that induced with colcemid and HAT which appeared as dicentrics
are also allocyclic chromosomes so the disruption of telomeric links
occur at the early stages of mitosis as telomeric fusion exists at the
interphase. Thus we conclude from our experiments that cell response
depends on type of HAT , specific properties of cells and mode of
1.Stobetsky V.I. (1976). Chromosome fusion by telomeres in cells treated
with colcemid and 5-bromodeoxyuridine. (Russ). Bull.Exptl.Biol.Med. No9.
2.Stobetsky V.I. (1978). Mammalian polykaryocytes in vitro.II.The
phenomenon of delayed disruption of telomeric links between chromosomes.
Biologisches Zentralblatt. 97:595-604.
3.Stobetsky V.I. (1995). Cytogenetic abnormalities in cultured human
lymphocytes undertreatment with halogenated analogs of thymidine.(Russ).
Bull.Exptl.Biol.Med. No9. 326-328.
Vladimir I. Stobetsky
Research Institute of Pediatric Hematology
Laboratory of Cytogenetics and Molecular Biology
App. 116, 6 Novoorlovskaya St. Moscow, 119633, Russia
tel: +7 095 731 8932
e-mail address: sto at aha.ru
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